1. Technical Field
The present invention relates generally to child-resistant closures, and more particularly to child-resistant closures with multiple caps which engage by radial contact offering advantages over the prior art by enabling easier opening, yet which remain child-resistant.
2. Background of the Invention
Today, child-resistant closures are very important for the safety of children. As used herein, use of the term "child-resistant closure" is consistent with 16 CFR 1700 and refers generally to the inability of a younger child's or person with a younger child's strength and/or manual dexterity to open a closure 85% of the time within a given amount of time without a demonstration of how to open the closure, or 80% of the time with such a demonstration.
There are presently many different child-resistant closure designs. Of the most common closures, those which have proven to work well are caps which require two or more concurrent motions in order to open them. For example, one such design is the "push-and-turn" closure. Generally, such closures can only be opened by simultaneously pushing downward on the cap while turning it.
Examples of "push-and-turn" designs are disclosed in U.S. Pat. No. 4,319,690, issued to Stewart H. Birrell and Peter Hedgewick on Mar. 16, 1982, and U.S. Pat. No. 4,394,916, issued to Ned J. Smalley on Jul. 26, 1983. These patents describe a typical two-piece, ramp and lug design. Essentially the closure comprises an inner cap and an outer cap which are rotatably attached to one another. A plurality of lugs on one cap project towards a plurality of corresponding ramps on the opposite cap. Generally, the ramps and lugs engage each other when turned in a fastening direction such that the two caps turn in tandem.
However, when the cap is merely rotated in an "unfastening" direction, the lugs tend to slide over the ramps. The outer cap turns freely from the inner cap, and the inner cap remains fastened to the container. In order to open the cap, the outer cap must be pushed downward in order to counteract the tendency of the lugs to slide over the ramps while the cap is being turned.
These cap designs tend to work well because children lack the strength, cognitive ability, dexterity and/or motor skills to make the required motions simultaneously. The dual motion closures thus prove to be not readily openable by children, and therefore effectively achieve the goal of preventing children from opening the container on which the closure is attached.
However, though the many child-resistant closures are effective at preventing children from opening them, the closures have also proven to be very difficult for others lacking strength and/or manual dexterity skills, though not necessarily to the same extent of a child. For example, seniors and others suffering from arthritis, loss of strength and other similar infirmities and disabilities may find such closures difficult to open. In the following description, closures which present such difficulties (e.g., 10% or more of seniors cannot open the closure within a given time) will be referred to generally as "senior-resistant" while closures which can be opened by such will be referred to generally as "senior-friendly".
Senior resistant closures are troublesome as quite often, seniors are the very persons in need of the contents (e.g., medication) sealed by the closure. However, because they may be arthritic or have a general lack of strength, coordination, dexterity, etc., seniors (and disabled or infirm) are not able to open the closure. In particular, though they may be able to make the simultaneous motions required to open the closure, the lugs typically engage the ramps through the range of contact at only one point or region of contact, away from the outer edge of the cap. This "point contact" coupled with the location of that point require that more torque and/or downward force be applied in order to remove the cap. Seniors often do not have sufficient strength or dexterity to both supply the extra torque required and push downward on the cap in order to remove the cap assembly. The closure thus becomes, in effect, senior-resistant as well as child-resistant.
Designers and manufacturers of child-resistant closures have long recognized the difficulty seniors have in accessing containers with child-resistant closures. However, no designs which overcome the effects of "point contact" have been developed, and similarly, no other designs which adequately prevent children from opening the closures, yet which allow seniors to open them have been developed.
For example, attempts to address such difficulties, so-called "arthritis caps", have been developed. These caps are designed to be more easily opened by arthritics. However, the caps suffer from being more readily openable by children as well. This is generally because as the closures became easier for seniors to open, to some extent, it becomes easier for children to open the closures as well. Such a result is unacceptable as preventing children from opening the closures outweighs the desire for seniors to have the ability to open the closure. Thus, true child-resistant caps remain a necessity.
Accordingly, a child-resistant closure which overcomes the drawbacks of point contact, which children cannot remove, yet which seniors can more readily remove is therefore desirable.